Straight Lines
Grade None
Question:
<p>The image of P (a, b) in the line x + y = 0 is Q and the image of Q in the line x - y = 0 is R, then the mid-point of PR is :</p>
<p style="display:inline">(a - b ,b - a)</p>
<p style="display:inline">(a + b, b + a)</p>
<p style="display:inline"><span class="math-tex">\(\left(\frac{a+b}{2}, \frac{b+a}{2}\right)\)</span></p>
<p style="display:inline">(0, 0)</p>
Step-by-Step Solution
Key Concept: Successive reflections of a point (a, b) across the lines y = -x and y = x result in the point (-a, -b), which is the reflection of the original point through the origin.
<p>(0, 0)</p>
Correct Answer: D